OP ARTS AND SCIENCES. 337 



The following equations of condition were obtained. 



It will hereafter be shown that at 32° 



7^=4- 102.8 /i = J. 

 But »49»_7^«^ =91.7 IX. 



Hence "49" + ll.l/x = A 



Forster gives for " 49 " the following relations : — 



From the direct comparison of the Berlin meter with the Metre des 



Archives, 



"49" + 21.4^ = ^. 



From a comparison of the Berlin meter with the meter of the Con- 

 servatory, 



«49"-|_ 5.2/x — J. 



It will be seen that the value found in terms of the Tresca meter 

 falls between these values. 



Since the absolute coefScient of expansion of " 49 " has been deter- 

 mined both by Forster and by Pierce, the relation here obtained be- 

 tween T and " 49 " will yield a value for T. We have for " 49," for 

 each degree Centigrade, 



Forster, 18.69 /x. 



Pierce, direct, 18.83 /x. 



Pierce, indirect, 18.81 fx. 

 VOL. xviii. (n. s. X.) 22 



